In a well coaxial conduits may be provided in a wellhead such as casing. A packoff seal is provided blocking off the flow through the annulus between the conduits in order to control the fluid therein. In order to test the packoff seal to determine whether or not the seal is correctly set, a testing plug is placed in the interior of the interior conduit, and as described in U.S. Pat. Nos. 2,951,363 and 3,872,713, pressure is applied to the top of the seal. If the pressure holds, the seal is good. If, however, the seal is not good, the pressure will pass around the seal and flow into the annulus between the two coaxial conduits and often collapse one of the conduits.
The present invention is directed to a method and apparatus for monitoring the annulus pressure between the coaxial well conduits to avoid undesirably high pressures in the annulus.